The present invention relates generally, to tissue characterization, and specifically, to a device and method for forming effective sensor-to-tissue contact, for tissue characterization.
The use of suction, for engaging a medical instrument to a tissue, is known. For example: U.S. Pat. No. 5,727,569 to Benetti et al., entitled: “Surgical devices for imposing a negative pressure to fix the position of cardiac tissue during surgery”, whose disclosure is incorporated herein by reference, teaches devices and techniques of using a negative (suction) pressure or vacuum, applied through surgical instruments for fixing the position of a portion of the surface of a beating heart so that a surgical procedure can be more easily performed. The devices apply negative pressure at several points on the outer surface of the heart such that a portion of the heart is fixed in place by the suction imposed through the surgical instrument. Because the instrument fixes the position of the tissue, and because the instruments remain at a constant distance from the particular portion of the heart where surgery is performed, the device may also serve as a support or platform so that other surgical instruments or devices can be advantageously used at the site. In certain preferred embodiments, the devices described are structured to facilitate the use of additional surgical instruments such that the placement of the negative pressure device permits the surgeon to advantageously manipulate the other instruments during surgery. The negative pressure is preferably imposed through a plurality of ports that may be disposed in a substantially planar surface of the instrument that contacts the cardiac tissue.
In addition, U.S. Pat. No. 5,927,284, to Borst, entitled, “A Method and Apparatus for Temporarily Immobilizing a Local Area of Tissue,” whose disclosure is incorporated herein by reference, describes temporarily immobilizing a local area of heart tissue to permit surgery on a coronary vessel in that area without significant deterioration of the pumping function of the beating heart. The local area of heart tissue is immobilized to a degree sufficient to permit minimally invasive or micro-surgery on that area of the heart. A suction device is used to accomplish the immobilization. The suction device is coupled to a source of negative pressure. The suction device has a series of suction ports on one surface. Suction through the device causes suction to be maintained at the ports. The device is shaped to conform to the surface of the heart. Thus, when the device is placed on the surface of the heart and suction is created, the suction through the ports engages the surface of the heart. The suction device is further fixed or immobilized to a stationary object, such as an operating table or a sternal or rib retractor. Thus, the local area of the heart near the suction device is temporarily fixed or immobilized relative to the stationary object while suction is maintained. In this fashion, the coronary artery may be immobilized, even though the heart itself is still beating so that a bypass graft may be performed. In addition, the suction device may be used in either a conventional, open-chest environment or in a minimally-invasive, endoscopic environment.
U.S. Pat. No. 6,728,565, to Wendlandt, entitled, “Diagnostic Catheter Using a Vacuum for Tissue Positioning,” whose disclosure is incorporated herein by reference, describes the use of a diagnostic catheter, associated with a vacuum source, for attaching a sensor to a tissue surface. The method includes inserting a catheter with a sensor at its distal end into the body of a patient, applying suction through the catheter, to draw tissue into a predetermined sensing position for the sensor, and analyzing the tissue with the sensor. The degree of vacuum may be adjusted, so that only the required amount of force is used to maintain contact between the sensor or sensors and the tissue being analyzed.
U.S. Pat. No. 6,090,041, to Clark, entitled, “Vacuum Actuated Surgical Retractor and Methods,” whose disclosure is incorporated herein by reference, describes a surgical retractor for retracting body tissue or organs, using suction. The surgical retractor includes an end piece adapted for sealing engagement with body tissue, the end piece having at least one suction port therein, the at least one suction port operably linked to at least one vacuum line. Suction supplied to the at least one suction port may be controlled by a vacuum control unit. Retractors of the invention may be provided in a range of shapes and sizes, according to the intended application or tissue to be retracted. A method for making a vacuum actuated retractor of the invention is disclosed, together with a method for automatically retracting body tissue.
U.S. Pat. No. 6,695,782 to Ranucci et al., teaches an ultrasonic tissue ablation device comprising a transversely elongated probe and a coupling assembly for probe attachment and detachment that enables the probe assembly and separation from the device body that includes the ultrasound energy source and sound conductor, and a method of use for removal of vascular occlusions in blood vessels. The coupling assembly enables incorporation of elongated probes with small cross sectional lumens such as a catheter guide wire. The probe can be used with acoustic and/or aspiration sheaths to enhance destruction and removal of an occlusion. The horn assembly of the device that contains a sound conducting horn functions as an energy regulator and reservoir for the probe, and precludes loss of probe cavitation energy by its bending or damping within the blood vessel.
U.S. Pat. No. 6,500,112, to Khouri, entitled, “Vacuum dome with supporting rim and rim cushion,” whose disclosure is incorporated herein by reference, describes the use of vacuum for tissue stretching, to enlarge a soft tissue, for example after a breast surgery, or to correct a deformity. It utilizes a generally rigid dome, capable of withstanding a pressure differential, with a rim cushion underlying the rim of the dome, for supporting the rim against the patient's skin surface. The rim may be generally wider than the dome in order to distribute the attendant forces across a greater surface and avoid tissue damage. A sticky sole underlies the rim cushion and seals the rim cushion to the patient's skin, to thereby preserve the vacuum within the dome. The sticky sole may be any adhesive material or be achieved through the use of an appropriate material for the rim cushion itself. Unlike the other references, described hereinabove, in U.S. Pat. No. 6,500,112, the vacuum is used for its therapeutic effect, i.e., tissue stretching, to enlarge a soft tissue or to correct a deformity, rather than as means for attaching another instrument.
Different types of sensors and probes for tissue characterizations are known and available today. Even though the operating principles of the different types of tissue characterization techniques differ, effective contact between the sensor and the tissue itself is often essential for reliable results. For example, the presence of air bubbles between an ultrasound tool and the tissue will interfere with ultrasound measurements. Similarly, a liquid layer may interfere with optical spectroscopy. There is thus a recognized need for devices and methods for ensuring effective contact between the sensor and the tissue, free of air, liquid and foreign matter.